Unidirectional gear drive



y 1946. c. w. HEWLETT, JR ,3 ,92

UNIDIREGTIONAL GEAR DRIVE Filed Dec. 20, 1945 V Ir'iventorr, Ciarerice W. Hewtett Jr;

Attorneg. z

'Patented May7,1946 V l y l UNITED STATES PATENT OFFICE 1 2,999,925 UNIDIBECTIONAL GEAR. DRIVE Clarence W. Hewlett, Jr., Marblehead, Mara, assignor to General Electric Company, a corporation of New Ijork Application December 20, 1943, Serial No. 514,934

Claims. (Cl. 74-437) My invention relates to unidirectional drive side of the teeth of uniform pitch or spacing as gearing and its object is to provide a gear drive in a normal gear. Hence, this direction of drive which performs its usual function while driving is normal and is the condition represented in in one direction, but which prevents operation Fig, 1.

in the opposite direction, or, if desired, permits 5 It now the driving gear be reversed so as 7 continuous normal operationin one direction and to rotate counterclockwise, it is seen that the permits normal operation in the opposite direcdriving surfaces of gear H are of unequal pitch tion except for a selected rotary position of the or spacing. When gear ll first starts to rotate gears. The direction for normal operation may counterclockwise from the position shown, it will be selected as desired when the gears are as- 1 drive gear ll until tooth a clears tooth h. Then sembled. tooth c will advance relative tb tooth d into The features of my invention which are bedriving contact with d as shown in Fig. 2 and lieved to be novel and patentable will .be pointed drive tooth d a small distance, bringing tooth e out in the claims appended hereto. For a better down on the top surface of tooth 1, thereby lock understanding of my invention, reference ismade ing the-gears from further driving operation in in the following description to the accompany this direction. Thus it is evident that gear Ill ing drawing in which Fig. 1 represents a'spur can only drive gear II with gear l0 rotating gear train including a one-way drive according clockwise. Ii gear ll be: used as the driving to my invention. Fig. 2 is a fragmentary view of gear, the uniformly pitched surfaces of the teeth the one-way drive of Fig. 1 explanatory of the zomust again be used as the driving surfaces, so locking operation. Fig. 3 illustrates a one-way that gear I I can only drive gear in with gear 8 l spur gear drive where the locking position is at rotating clockwise and if attempt is made to a selected point of the larger gear. Fig. 4 illusreverse the direction of drive, the. locking action trates a further modification of the invention; will occur,. 'By simply turning gear ll over, the and Figs. 5 and 6 are included to show that the locking actions above described will occur tor invention is applicable to internal, and worm directions of operation reverse to those described gearing. Fig. 7 showsconventional gears modiabove. No locking action occurs between gears v fied in accordance with my invention. H and I! for either direction of operation be-' Referring now to Fig. 1; Ill, ii, and i2 repre-- cause the intermeshing contact occurs between sent the spur gears of a gear train for transfera sufllcient number of teeth that relative disring rotary motion between diiierent shafts at placement of the gears does not occur. Thus selected speeds, depending on the gear ratios tooth g is prevented from contacting the surface used. If gear 'III is assumed to .be the driving of tooth it because of the driving engagement of gear rotating in a clockwise direction, gears II the teeth to the left. However, a locking gear and I2 willbe driven counterclockwise and clock arrangement according to my invention could wise, respectively, in the usual manner. Howbe made between gears ii and I! by cutting oflf ever, it attempt .is made to drive gear ll from the same side of a pair of corrective wide teeth. gearll with the latter rotating counterclock- Thus if wide tooth i were cut off as indicated in wise, the gears will look. It gear ll be considdotted lines, a locking action would occur here cred the driving gear, it will drive gear II only if gear, rotating counterclockwise, was driving in a counterclockwise direction, but it will drive gear ll. Thus the invention is applicable both gear l2 in either direction. It is noted that gear to gears which mesh with only one driving tooth H has alternate peripherally wide and narrow at a time as between gears II and H, or with teeth and alternate peripherally wide and nargears where several teeth mesh as between gears row recesses between the teeth. This tooth tor- "II and I2, and the same gear ll may mesh with mation may be obtained by using a wide toothed both types of gears with only one type performgear and cutting off from a half to two-thirds 1 ing a locking action. In'any case where a lockof the same side of every other tooth. Thus ing action occurs, the gears arelocked only in Fig. 3 shows such a wide toothed gear at I I the locking direction and can be unlocked in with only one tooth ll thus cut off. The gears 'that direction by making the driven gear the II and I! have narrow teeth and wide recesses. driving gear.

If gear ll be considered as being driven by gear Thus itis seen that thisiorm of one-way gear III, with the latter rotating clockwise, it may be drive is quite flexible as to its manner of use stated that the iront'of every other tooth of gear and application and can b v applied quite gen- II is cut off, leaving the back or driving surface erally in a gear train by providing gears having the tooth arrangement described. It may be used, for example, in a sell-starting. single-phase synchronous motor drive where the motor may start in either direbtion but only a selected direction of operation is desired.

It should be mentioned that where the oneway gear drive is employed to drive a load of the spring type as, for example, the winding of a spring, and the gear stops and reverses, the locking action will not occur until the back spring torque ceases because in such case, the spring in eilect becomes a backward driving force to prevent shift oi the gears to lockin relation. Thus the device is not a substitum to a ratchet to prevent the spring from unwinding in a spring winding device.

Another limitation to e observed is explained as follows: Considering gears I and ll of Fig. 1, ii I0 is the driving gear rotating counterclockwise driving gear II, and gear ll tends to overrun gear It for any reason, as might be the case if gear III were slowed down suddenly, the gears will shift and lock. Hence, there is this possibility of locking action in both directions oi rotation when gear I0 is the driving gear. However, if gear Ii is the driving gear rotating clockwise, and gear l0 tends to overrun, there is no locking action. In this case tooth e would strike the top of tooth and momentarily stop geare but tooth J can still move clockwise from under tooth e and resume the drive. Hence, where an overrun of the driven gear is likely to occur, it is best to make the gear having the difierent kinds of teeth, such as the gear H in Fig. 1, the driving gear because then no locking action can occur in the normal drive direction.

, In any case where it is desired to have the looking occur at a particular point in the rotative position of the gears, the gear teeth will be modified for locking action only at such selected point. Thus in Fig. 3 only one tooth H of gear it has been cut off so that locking can occur only when 7 gear drive modified to provide locking in one direction in accordance with my invention. Here we front side of one tooth in gear I! has been cut back and the back side of one tooth in gear l8 has been out back. If gear II he considered the driving gear and rotating clockwise, the drive is normal with the gears in correctly meshed relation. If, however, drive gear I8 bereversed, the extra backlash permitted by the cutaway part of the normal teeth, which is all in a direction away from a correctly meshed relation, is suificient to bring the ends of the normalteeth to the right into locking engagement instead of into proper meshing engagement.

If in Fig. '7 the gears I1 and i8 beassumed to be of the same diameter and have the same number of teeth, the cutting away of the teeth in one direction alone is not suflicient to produce locking in either direction. Hence, if such gears were assembled where the cut-oil portions of the teeth in both gears never meshed, there would be no locking action. If, now, the gears be assembled as shown but it be assumed that gear i8 is twice the diameter and has twice the number of teeth as gear i'l then we would have locking action in one direction of rotation for each revolution of the large gear but for every other revolution of the small gear. Again if one gear had fifty teeth and the other forty-nine locking action could occur only when the out ch teeth came into mesh or about fifty revolutions. This example will indicate the additional flexibility and application of my locking gear invention.

this tooth is in'meshing relation with gear it).

For another application I could cut oil the opposite side of another large tooth of gear i3, Fig.

3, as indicated at m. With such an arrahgement gear it could drive gear IS in opposite directions between teeth H and its measured the long way around between them or for about threegenerally satisfactory where from one half to two-thirds of alternate large teeth are out ch, or in the case where several teeth mesh. as between gears H and I: of Fig. 1, two consecutive large gear teeth may be cut oil for a locking action. The best amount of cutting oil will depend somewhat on the height of the teeth and the diameters and types of the gears employed but the exact amount is not critical.

In Fig. 5 an internal one way locking gear is shown, and in Fig. 6 a one-way worm gear drive is shown which becomes locked when the gear wheel is driven by the worm in a counterclockwise direction.

In accordance with the provisions of the patent statutes, I have described the principle of operation of-my invention together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a gear drive a pair of intermeshed gears, one having uniformly spaced peripherally narrow teeth and the other having alternate peripherally wide and narrow teeth, the narrow teeth being from one-third to one-half the peripheral width or the wide teeth and so spaced that the gears 1 function in a normal manner when the drive is in a given direction but look when the direction of drive is reversed.

2. In a gear drive a pair .of intermeshed gears, one gear having peripherall narrow teeth and the other gear having peripherall wide teeth, said wide toothed gear also having at least one peripherally narrow tooth of irom one-third to one-half the width of a wide tooth and positioned as it formed by cutting ofl one side of a normally spaced wide tooth such that corresponding sides of the teeth in the gear having the wide and narrow teeth have an equal'tooth pitch spacing but the reverse sides have an unequal tooth pitch spacing which causes locking when such reversed sides are used as the driving surfaces.

. 3. A one-way drive gear havingalternate peripherally wide and narrow teeth, a narrow tooth being between one-third and one-half the width of a wide tooth, said teeth being positioned so that one side ofall teeth have a uniform toothexcept at one point oi its toothed suriaoe where it has at least one peripherally narrow tooth between one-third and one-half the width of the wide teeth having one side surface uniiormly spaced with respect to corresponding sides of the wide teeth.

5. A one-way gear drive comprisin: a pair of gears the teeth of which are continuously intermeshed and with the peripheral sides of the teeth on one side in both gears evenly spaced so as to permit oi assembly and normal continuous drivin: operation between said gears in one direction where said evenly spaced gear teeth sides ensase in driving relation, the peripheral tooth width of said gearing being reduced below normal in at least one position 0! engagement of said sears by an amount to allow extra backlash in the searing oi the order of one-half tooth pitch whereby whencontinuous drivin: operation between said sears is attempted in the other direction the sears rotate relative to each other when in such position oi engagement until they are improperly meshed by. an amount corresponding to said extra backlash wherebythe outer ends of normal peripheral width teeth in the two sears which are adjacent to and approaching said position of engagement collide to lock the gears against further driving operation in said other direction.

CLARENCIW. BEWIBTT, JR. 

